The present invention relates generally to hybrid vehicles and more particularly to an electric hybrid four-wheel drive vehicle.
The powertrains of conventional vehicles are designed to provide more power than required for the vehicle at cruising speeds. Specifically, the engine of conventional vehicles is larger than required to provide power for acceleration and hill climbs. This extra power is not required once the vehicle is at cruising speed. As a result, conventional vehicle powertrains are inefficient.
Therefore, it is desirable to have an improved vehicle powertrain for implementation in a vehicle, such as a hybrid vehicle, which overcomes inefficiencies inherent in a conventional powertrain.
Additionally, various types of continuously variable transmissions (CVTs) have been developed throughout the years. The object of a CVT is to provide a continuously variable drive ratio from a transmission enabling an engine to run at an optimum point on a brake specific fuel consumption curve. Essentially, CVTs aim at improving engine efficiency by enabling the engine to continuously run at its most efficient point. Due to the significant complexity, traditional CVTs have posed problems in both implementation and application. Traditional belt drive-type CVTs are also inefficient in that significant parasitic losses occur in achieving continuously variable transmission ratios. Moreover, such devices are power limited.
Therefore, it is desirable in the industry to provide an improved CVT for implementation in a vehicle, such as a hybrid vehicle, which overcomes the deficiencies of traditional CVTs.
In achieving the above identified objectives, the present invention provides a continuously variable transmission comprising a first planetary gear set, a second planetary gear set operably coupled to said first planetary gear set, an input shaft rotatably coupled to each of the first and second planetary gear sets for selectively providing a drive torque, an output shaft rotatably coupled to the second planetary gear set, a first electric motor operably coupled to the first planetary gear set for selectively functioning to one of either rotatably drive the first planetary gear set and retard rotation of the first planetary gear set, and a second electric motor operably coupled to the second planetary gear set for selectively functioning to one of either rotatably drive the second planetary gear set and retard rotation of the second planetary gear set. The first and second electric motors cooperate to selectively manipulate rotation of the first and second planetary gear sets for varying a drive ratio between the input shaft and the output shaft.
The present invention further provides a hybrid vehicle comprising an engine, the above-described transmission operably attached to the engine, and a first driveline operably interconnected with the output shaft for driving a first wheel. The hybrid vehicle may further comprise a second driveline operably interconnected with the output shaft for driving a second wheel, thereby providing a multi-wheel drive vehicle.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art.